Changes in marine ecosystems attacked by the mega-earthquake and subsequent massive tsunami

on Pacific coast of northeast Japan

Tomohiko Kawamura 河村知彦

Coastal Ecosystem Restoration, International Coastal Research Center,

Atmosphere and Ocean Research Institute (AORI), The University of Tokyo

東京大学大気海洋研究所・国際沿岸海洋研究センター・生物資源再生分野

International Coastal Research Center,

AORI, The University of Tokyo

東京大学大気海洋研究所

国際沿岸海洋研究センター

Otsuchi Bay大槌湾

Otsuchi, Iwate岩手県大槌町

International Coastal Research Center AORI, Univ. of Tokyo at Otsuchi, Iwate

The maximum tsunami height: 12.2 m

�All of the staffs and students escaped unhurt. �Some of the local staffs lost their houses.�All buildings and facilities were completely destroyed or damaged.�1300 people were killed or still missing out of ~15000 in the town.

International Coastal Research Center AORI, Univ. of Tokyo at Otsuchi, Iwate (after tsunami)

6

International Coastal Research Center AORI, Univ. of Tokyo at Otsuchi, Iwate (May, 2013)

What happened in coastal ecosystems, and in the populations of fisheries resource organisms?

Tohoku Ecosystem-Associated Marine Sciences (TEAMS) funded by MEXT, Japan (2012-2021)

文部科学省補助事業・東北マリンサイエンス拠点形成事業

Analyze effects of the earthquake and tsunami on marine ecosystems and subsequent recovering processes, to restore and develop fisheries

AORI, Univ. Tokyo(Otsuchi Bay, Sanriku Coast) Subject 2: Changes in

coastal ecosystems

JAMSTEC(Offshore seafloor)Subject 3: Changes in offshore seafloor ecosystems

Tohoku Univ.(Onagawa Bay, Sendai Bay)Subject 1: Changes in fishing

and aquaculture grounds

Iwate Univ.

Tokyo Univ. Mar. Sci. Tech.

Tokyo Univ. Mar. Sci. Tech.

Kitasato Univ.

Tokai Univ.

Subject 2: Changes in coastal ecosystems (AORI, Univ Tokyo)

②Changes in communities and populations of organisms

③Changes in the material cycle

①Establish monitoring/analyses tools

④In flux of environmental pollutant

⑦Ecosystem modeling for rebuilding fisheries

Analyze and monitor ecosystems and environments

⑤Effects of forests and rivers on coastal marine environments

⑥Physical environments in coastal ecosystems

Estuary mudflat

Tohoku Ecosystem-Associated Marine Sciences (TEAMS)Subject 2: Changes in coastal ecosystems ② Changes in communities and populations of organisms

(by over 100 scientists and students)�Studies on various coastal ecosystems

Intertidal rocky reef Subtidal algal bed

Seagrass bed Offshore seafloor Salt marsh

�Studies on various communities and populations

Ayu Pacific Herring Chum Salmon

Ezo Abalone

Finless Porpoise

Sea urchins Manila clam

Benthos communityStreaked Shearwater

Seagrasses

Macro-algae

12

Seagrass communitiesアマモ群落

July, 2010

October, 2011Photos were taken by Prof. Nakaoka

Otsuchi Bay

2010 2011

（Seike et al. 2013)

Changes in mega-benthos distribution in Fanakoshi Bay after the tsunami

2012

� Sand dollars (~5 cm diam.), found in high density in 2010,almost completely disappeared after the tsunami in 2011.

Tomarihama, Oshika Peninsula牡鹿半島泊浜

Otsuchi Bay 大槌湾

ICRC, AORI, Univ of Tokyo

Organisms on shallow rocky reefs have been studied and monitored seasonally for over five years.

Tomarihama, Oshika Peninsula

5 km 50 m

Macroalgal zonation海藻帯状構造

(Tomarihama 泊浜)

Algal turfstransitional zone

Red algae: Gelidium elegans小型紅藻群落

Eisenia Kelp bed 2 - 4 m depth

Brown alga: Eisenia bicyclisアラメ群落

CCA bed> 5 m depth

Crustose Coralline Algae: Lithophyllum yessoensis

無節サンゴモ群落

38゚20

' N

November, 2010

June, 2011

Remaining Eisenia holdfasts that lost their fronds were observed in Kelp bed, but Eisenia biomass has not significantly decreased after tsunami.

Kelp bed アラメ群落

2 - 4 m

38゚20

' N

November, 2010

June, 2011In CCA bed, many large rocks were cracked and rotated, and bare rocks without any epibiota and CCA emerged.

CCA bed サンゴモ群落

> 5 m

Abalone エゾアワビ

Haliotis discus hannaiSea urchin キタムラサキウニ

Strongylocentrotus nudus

Spawning放卵・放精

Fertilization受精

Metamorphosis 変態

Larva 浮遊幼生

Post-larva 初期稚貝

Juvenile稚貝

Adult 成貝

Life cycle of abalone

CCA bed サンゴモ群落

Algal turfs 小型紅藻群落

Kelp bed コンブ類群落

Ontogenetic habitat shifts in abaloneH. discus hannai

Adults (> 4 cm SL)Settlement - 2 cm SL Juveniles (2 - 4 cm SL)

0

1

2

3

4

5

6

7

アラメ 境界 CCA

生息

密度

(in

ds/

m2)

2010年7月

2010年11月

2011年2月

2011年6月

Kelp bed アラメ CCA bed サンゴモ

Den

sity

(indi

vidu

als/

m2 ）

（after the tsunami)

Algal turfs 小型紅藻

Jun 2011

Feb 2011Nov 2010

Jul 2010

ab

ab a

b

Adult abalone (> 5 cm) mainly in Kelp bed decreased by ~50%.Juvenile abalone mainly in CCA bed decreased by ~90%.

Abalone densities (Oshika peninsula)エゾアワビ個体数密度（牡鹿半島） (Takami et al. 2013)

�Densities of juvenile abalone (< 5 cm SL) largely decreased.

Recruits to the fishery resource will largely decrease for 3 -4 years.

*Reseedings have stopped and may not be opened for several years.

Abalone size distribution (Oshika peninsula)エゾアワビ殻長組成（牡鹿半島）

Shell length (mm)

0

10

20

30

40

0 10 20 30 40 50 60 70 80 90 100 110

2011年2月9日

n=90

0

10

20

30

40

0 10 20 30 40 50 60 70 80 90 100 110

2011年6月8日

n=23Jun 2011(n = 23)

Feb 2011(n = 90)

(Takami et al. 2013)

0

5

10

15

20

25

30

アラメ 境界 CCA

生息

密度

(in

ds/

m2)

2010年7月

2010年11月

2011年6月

（after tsunami)

Jun 2011Nov 2010

Jul 2010

Kelp bed アラメ CCA bedサンゴモ

Den

sity

(indi

vidu

als/

m2 ）

Algal turf 小型紅藻

Sea urchin densities (Oshika peninsula)キタムラサキウニ個体数密度（牡鹿半島）

Sea urchin density in AT and CCA decreased by ~95%.

a

ab

a a

bND b

(Takami et al. 2013)

Short-time effects by the earthquake and tsunami�Different species/growth stages of organisms had different effects.

Organisms with weaker adhesive strength decreased more.

Organisms inhabiting CCA decreased more than those in KB.

The changes in community structure and balance of organisms

may affect ecosystems for a long time.

Long-time effects by the earthquake and tsunamiLand subsidence, Sea level rise 地盤沈下、海面上昇

→ Continuous sedimentations→ Negative effects on settlement of larvae and zoospores

Destructions of seagrass bed and mud flat 海草群落・干潟の減少

→ Changes in transparency and nutrient concentrations (?)→ Effects on algal/seagrass growth/survival/species composition

Changes in species composition of animals 動物組成の変化

→ Changes in community and food-web structures (?)

What are important to conserve marine ecosystems and utilize fisheries resources continuously and efficiently

in the disaster area?

�Exactly understand the effects of the earthquake and tsunami on marine ecosystems, monitor their secondary succession processes, and clear their mechanisms.

�Consider suitable styles of fisheries and utilizations of fishing grounds adapting the succession process of ecosystems, and establish new measures for fisheries and resource managements.

�Any human activities should be conducted carefully based on the scientific guidelines to minimize further negative effects on the damaged ecosystems, and not to prevent the natural recovery.

＊Nature can be easily destroyed by human activities, but very difficult to be restored!!

＊Huge impacts of fishery activities on marine organisms!